plainsong

Traditional single-line chant melodies used for singing the texts of the Christian church. Plainsong was first adopted by Ambrose, Bishop of Milan, and then by Pope Gregory in the 6th century, the latter being referred to as Gregorian chant. It is properly sung in unison, without harmony and with no definitely measured rhythms. Its groupings of notes have, however, a strongly rhythmic character, but it resembles the free rhythm of prose, whereas that of measured music is comparable to the rhythm of verse. The old notation on a stave of four lines, with square or diamond-shaped notes and ligatures, is still used for plainsong.